I used Colorback polish on a pretty rough Jeunet my neighbor put out for trash pickup. With a little elbow grease it did a great job removing many years of old grime and the paint ended up looking pretty nice. There might be better stuff, but I happened to have it on hand. Sorry, no before and after pics.

I've got two chrome fenders. The outside looks nice but I need to clean up the inside part. Doesn't have to be perfect, but it's loaded with rust and want to get it off. WD40 again?

You could pour a bit of oxalic acid solution into it, and move it around until each section has had a couple hours to soak. WD-40 is good at removing the older rust, but the acid stops rust in its tracks.

I've used something called "paint renovator" with some success. It's basically a very mild buffing compound in a liquid state. Go easy, and start on the underside of the frame. If you see much color on your cloth, discontinue - you're removing too much paint. You could probably buy a bit of something similar from a local body shop. Then use a good auto wax and you should be in business.